Piezo-electric device



June 8 1926. 1,588,176

A. L. R. ELLIS PIEZO ELECTRIC DEVICE Filed July 14, 1925 Figi 6 Inventor:

Alvarado LREHS,

H is Attorney.

A'Patente-rl June 8, 1926.

UNiTED STATES PATENT OFFICE.

ALVARADO L. R. ELLIS, OF SWAMPSCOTT, MASSACHUSETTS, ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

PIEZO-ELECTRIC DEVICE.

Application filed July 14, 1925. Serial No. 43,630.

My invention relates to devices comprising a piezo-electric member interposed between a pair of electrodes, andhas for its principal object the provision of` an arrangement 6 wherein the undesirable effects of the electrodes on the free vibration eriod of thepiezo-electric member are avoi ed orV greatly reduced.

The free vibration period of a piezo-elec- 10 tric oscillator, such as a slab or disk of quartz for example, -is determined for the most part by the dimensions of the slab but is affected to some extent by its mounting and by variation in the conditions under which it is operated. If it were possible-to suspend a piezo-electric oscillator in the air so that it could be made to oscillate freely, a layer of air adjacent its vibrating surfaces v would oscillate just as though it formed gn integral part of the piezo-electric memer. oscillator be provided with some sort of a mounting and it is desirable that it be protected from dust and moisture by a suitable casing. The mounting and casing, however, are likely to prevent free movement of the oscillator surfaces and 'the layer of air associated therewith and to produce variation in the resonance frequency of the oscilla- 30. tor. In accordance with my invention, this difficulty is largely avoided by the provision of electrodes formed and mounted in a man- A ner .to permit ready movement of the oscillator surfaces and the layer of air adjacent thereto.

O My invention will be better/ understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out sin 40 the appended claims.

Referringtorthe drawings, Fig. 1 shows al piezoelectric device wherein my invention has been embodied; and Fig. 2 shows a modiication thereof.

Fig. lshows a piezo-electric member l supported upon an electrode 2 which is mounted ron an insulation base 3and is connected to a terminal 4 through means shown as a screw 5. An electrode 6 located adjacent the upper surface of the member 1 is spaced from the base 3 by a conductive ring 7 and is connected to a terminal 8 through means shown as a screw 9, the electrode 6 and ring 7 be- It is of course necessary that the-I ing shown as cut away to expose the piezoelectric member 1 and electrode 2 which are located in the chamberk formed by base 3, electrode 6 and ring 7 In order to simplify the drawing, the electrode 6 has been shown as located at some distance from the oscillator 1. It should be understood however that in an actual construction the spacing between the oscillator l and electrode 2 is but a few thousandths of an inch.

In order to permit ready movement of the air adjacent the upper surface of the oscillator 1, the lower surface of the electrode 6 is slotted transversely and longitudinally or otherwise constructed to form small areas Aspaced apart to reduce the friction incident to movement of the air between it and the surface of the oscillator. With these small areas the air moved due to change in the thickness of the oscillator has to traverse the thin air gap between' electrode 6 and oscillator 1 only a short distance before it encounters one of the slots; the in and out flow of the air produced by vibration of the oscillator surfaces is greatly facilitated; and the effect of the mounting on the resonance frequency of the oscillator is correspondingly reduced.

Fig. 2 shows an embodiment ofthe invention wherein the oscillator l is-interposed between electrodes 10 and 11 which are made of perforated metal, wire gauze, or the like. This constructon like that of the arrangement of Fig. 1 has the advantage that the electrodes may be placed very close to the oscillator without interfering to any considerable extent with the movement of air adjacent its surfaces.

The embodiments of the invention illustrated and described Vherein have been selected for the purpose of clearly setting forth the principles involved. It will be apparent, however, that the invention is susceptible of being further modified to meet the dierent conditions encountered in its use and I therefore aim to cover by the appended claims all modifications within the true spirit and scope of my invention.

What I claim as new and desire to secure vby Letters Patent of the United States, is:

1. The combination of a piezo-electric oscillator, and an electrode having a plurality 105 of surface areas located adjacent a surface of said oscillator whereby the friction incident to the movement of air between the surfaces of saidoscillator and said electrode is` reduced.

2. The combination of a piezo-electric osciliator, and 'electrodes mounted adjacent opposite surfaces of 'said 'oscillator and provided with a plurality of surface vareas whereby the eti'ect of said electrodes on the ig'iss'eme free vibrating period of said oscillator fis 10 electrodes.

velectric oscillator interposed between said In witness whereof, I have hereunto set my hand this 10th dayoJuly, 1925. ALVARADO L. R. ELLIS. 

